This invention relates to an integral type thrust bearing in which a bearing ring and a retainer for housing rollers are mounted inseparably.
Among thrust bearings, there is an integral type in which the bearing rings and the retainer for housing the rollers are mounted inseparably from each other so that the thrust bearing can be easily mounted in a housing or on a shaft.
FIGS. 10A and 10B show an example of such an integral type thrust bearing. It is a three-part type bearing having a retainer 2 for radially housing a plurality of rollers 1, an inner ring 3 having a flange 3a on the inner-diameter side, and an outer ring 4 having a flange 4a on the outer-diameter side. The inner and outer edges of the retainer 2 are engaged by outwardly protruding claws 5 and inwardly protruding claws 6 formed by staking at the tips of the flanges 3a and 4a, respectively, so that the inner and outer rings 3, 4 and the retainer 2 are inseparable from each other. Among integral type thrust bearings, there are two-part type bearings which include only one of the inner and outer rings and the retainer is inseparable from the inner or outer ring.
In these integral type thrust bearings, the bearing rings, retainer and rollers are individually heat-treated beforehand, and thereafter, they are assembled into an integral unit. Normally, the bearing rings and the retainer are subjected to carburizing, hardening and tempering after forming. The rollers are hardened and tempered after rough forming, and then subjected to finish grinding. The retainer is in some cases subjected to soft nitriding instead of carburizing, hardening and tempering.
With such a conventional integral type thrust bearing, since the bearing rings, retainer and rollers are individually heat-treated before assembling, heat treatment steps increase, so that the heat treatment cost increases. Also, the manufacturing period tends to be long for adjustment of heat treatment steps for the respective parts.
In order that even if a radial gap in the bearing increases, the bearing rings and the retainer can be made inseparable to increase the eccentricity allowance of an integral type thrust bearing, the present applicant proposed in JP patent application 2001-272336 to form the flanges of the bearing rings by bending instead of staking, thereby increasing the protruding amounts of the claws. In order to form such markedly protruding claws by bending, such bending has to be carried out after the retainer has been mounted. Thus, during heat treatment of the bearings, it is necessary to prevent hardening of the portions to be bent, or add a step of annealing the bent portions after heat treatment.
An object of this invention is to reduce heat treatment steps in the manufacture of an integral type thrust bearing.